Tiller Population Research Articles

Structural and production characteristics and nutritive value of two tropical grasses submitted to different levels of nitrogen

The objective of this study was to evaluate increasing levels of nitrogen on and production and nutritive value of Andropogon and Massai grasses under the edaphoclimatic conditions of the Brazil denominated Middle Nort Region. The design used was completely randomized, with sixteen replicatios. The treatments consisted of nitrogen rates: 0, 150, 300, 450 and 600 kg N ha-1 and two forages, which were evaluated independently. The grasses used were Panicum maximum cv. Massai and Andropogon gayanus cv. Kunth. For Andropogon grass, there was an effect of nitrogen fertilization on thecharacteristics: leaf elongation rate, stem elongation rate, leaf senescence rate and leaf blade final length and, in all cases, the behavior was quadratic. Nitrogen also influenced the morphogenic characteristics: leaf appearance rate, leaf elongation rate, leaf senescence rate, phyllochron, leaf blade final length, number of live leaves per tiller and It was not significant for tiller population density of Massai grass, but the behavior varied according to the characteristic, in which leaf appearance rate and number of live leaves per tiller had decreasing linear behavior, while in phyllochron it increased linearly as nitrogen doses increased. Most of the productive characteristics of the grasses had increasing linear behavior (total biomass production of forage, leaf biomass and stem biomass in Andropogon grass, while in Massai grass, only the total forage production and dead material accumulation had an increasing linear behavior with increase of N doses. Quadratic effect only for masai leaf biomass behavior and there was practically no production of stems, affecting the leaf-stem ratio ) while the highest efficiency of nitrogen utilization was achieved with the application of 150 kg N ha-1 for the two grasses. Nitrogen fertilization also favored the nutritive value of the two grasses positively, with linear increase for crude protein and mineral matter contents, only in Massai, and reduction in the contents of neutral detergent fiber, acid detergent fiber and hemicellulose of grasses. Increasing doses of nitrogen fertilization favors the production, structure and chemical composition of the two grasses. However, the highest efficiency of use is obtained with the application of 150 kg N ha-1.

Growth Analysis in Sugarcane Ratoon Crop as Influenced by Potassium Nutrition in Subtropical India

ABSTRACT A field experiment was conducted for two cropping seasons during 2016–19 at the ICAR-Indian Institute of Sugarcane Research, Lucknow, Uttar Pradesh, India, with the objectives to study the effect of i) K nutrition and variable sources of K on growth analysis of sugarcane ratoon crop, ii) the response of K on the photosynthetic rate of crop and iii) contribution of K on yield attributes, sugarcane, and sugar yields. Mean results of two cropping seasons indicated that the application of potassium brought forth a 12.08% improvement in tiller population over no K (107.3 thousand/ha). Potassium application through K2SO4 (SOP) showed the highest net rate of photosynthesis (15.28 µmol/m2/s) which was about 30.71% higher than the control. Among the various sources of K, SOP was found the best in improving sugarcane and sugar yields. Application of SOP resulted in 18.69% ratoon cane yield improvement over the control. Application of 75% K through K2SO4 resulted in a higher sugar yield (12.01 t/ha) which was 25.76% higher than the control (9.55 t/ha). Potassium ammonium sulfate (PAS) and murate of potash could not produce better results as compared to K2SO4. Potassium application through SOP showed the highest net rate of photosynthesis (15.28 µmol/m2/s) during the grand growth phase. Application of 50.4 kg K/ha (75% more than recommended) through K2SO4 increased 18.69% sugarcane (106.7 t/ha) and 25.76% (12.01 t/ha) sugar yields over the control (no K) and was found to the best and could be recommended for improving sugarcane and sugar yields of ratoon in subtropical India.

Functional contribution of two perennial grasses to enhance pasture production and drought resistance under a leaf regrowth stage defoliation criterion

AbstractLolium perenne L. (Lp) is the main pasture species in New Zealand, but climate change increases the likelihood of drought during summer and consequently lowers its growth rates. Bromus valdivianus Phil. (Bv) tolerates better the summer soil water restriction, but its competitiveness in a diverse pasture relates to the defoliation management and soil moisture levels. The performance of both species in terms of production, persistence and feed quality across seasons under different defoliation regimens was evaluated when the species were mixed and in monoculture. The treatments were applied in a randomised complete block design with three blocks. Bromus valdivianus and Lp monocultures and the 50/50 mixture (Mx) were grazed at low and high defoliation frequencies (i.e. based on Bv and Lp optimal leaf regrowth stage [LS], respectively). Herbage mass production was 15% higher in the Mx, mainly due to an increase in production in spring and summer. In spring, there was complementarity growth between the species, while during summer/early autumn, the Mx production relayed in the higher participation of Bv. Root biomass at depth (31–70 cm) was 38% greater for Bv monoculture and the Mx compared with Lp monoculture, which demonstrated the contribution of Bv to a better production of the mixture during and following the dry periods. In addition, the maintenance of the Bv tiller population and the higher growth rate during dry periods demonstrated its better fitness to low soil water availabilities than Lp. Although herbage mass was not modified by the defoliation frequency, forage quality of Bv showed values at low defoliation frequency that could compromise animal production during spring. However, there was an increase in root biomass under low defoliation frequencies, which suggested that a flexible grazing management across seasons would increase the niche utilisation between species in the mixture. The defoliation frequency of the mixture could be based on Lp LS during spring and winter, and slowed down, following Bv criteria, during summer and autumn.

Tussock and tiller population dynamics on rotationally stocked Piatã palisadegrass (

Context Integrated crop–livestock–forestry systems can be an alternative to monoculture pastures; however, the effect of the arboreal component on tillering and tussock dynamics of understorey grass canopy is not well understood. Aims Our objective was to evaluate the patterns of tillering dynamics, population stability and tussock distribution of Piatã palisadegrass (Urochloa brizantha) as affected by contrasting shading regimes in the Brazilian Amazon biome. Methods The following three shading regimes were assessed: pasture with no trees (no shading, NS), moderate shading (MS, 338 trees ha−1), and intense shading (IS, 714 trees ha−1). Pastures were rotationally grazed by dairy heifers. Paddocks from MS and IS were stratified into three sampling strips, including two closer to the tree rows (i.e. lateral) and one between the two lateral strips (i.e. central). Two methods for monitoring sward canopy light interception (LI) were used for IS regime, namely, LI taken under the tree canopy (i.e. inside) and LI was taken above the tree canopy (i.e. outside). Key results Relative to NS, there was a reduction in photosynthetically active radiation transmittance of 18.1% and 37.1% on MS and 49.9% and 52.0% on IS for central and lateral shading strips respectively. Overall, the increase in shading level was associated with a decrease in average tussock perimeter, tiller population density, and an increase in the frequency of bare ground. Conclusions Our findings clearly indicate the key role of the light environment as a determinant of Piatã palisadegrass horizontal structure. Implications It highlights the importance of planning the levels of tree density and layout in areas of crop–livestock–forestry integration.

Características morfogênicas e estruturais de perfilhos e acúmulo de forragem do capim-tanganica sob níveis de sombreamento

ABSTRACT This study aimed to evaluate the effect of tree shading levels on tillers’ morphogenetic and structural traits, besides the herbage accumulation of Tanganyika grass ( Megathyrsus maximus Jacq. cv. Tanganyika). For that, an experiment was carried out from December 2010 to March 2012, under a completely randomized design, with four treatments (shading levels) and five repetitions. Phyllochron (PHY), leaf and stem elongation rates (LER and SER, respectively), number of leaves per tiller (NLT), leaf blade length (LBL), stem length (ST), tiller population density (TPD), leaf (LGR) and stem growth rates (SGR), senescence rate (SR) and herbage accumulation rate (HAR) were assessed. Excepted by the LER and NLT, the shading levels influenced the other morphogenetic variables (P<0.05), positively or negatively. Except in the spring, the TPD linearly increased because of the shading levels (P<0.05). At tiller level, except in the spring, the LBL linearly increased with the shading levels (P<0.05). In general, the SL linearly decreased with the shading levels. Regarding the growth rates, summer II and spring provided greater values, and the lowest one occurred in autumn (P<0.05). The adjustments of both morphogenetic and structural traits ensured the Tanganyika grass a great adaptation to the shaded environment.

Non-thermal plasma application improves germination, establishment and productivity of Gatton panic grass (

Megathyrsus maximus (Gatton panic) is a tropical grass highly valued both for its use as forage and for its biofuel potential. A major constraint in establishing pastures of this cultivar is the low viability and germination of seeds and the poor initial seedling establishment. We used non-thermal plasma (NTP, partially ionised gas) as a novel technology to treat seeds of this grass, aiming to improve their quality (i.e. germination traits). We also followed the performance of seedlings grown from NTP-treated seeds under field conditions by assessing seedling establishment, biomass production and forage quality during the first regrowth period, which is the critical period for pasture establishment. Two NTP treatments were performed through dielectric barrier discharges employing N2 as carrier gas. Non-treated seeds served as the control. Results showed that the viability of NTP-treated seeds was, on average, 1.5-fold higher than the control, and that germination energy and germination percentage of treated seeds was superior to the control by 2.1-fold and 2.2-fold, respectively. A field experiment showed that seedling establishment parameters (dynamics of cumulative emergence, emergence coefficient, and weighted average emergence rate) and pasture early productivity (represented by shoot dry matter) were enhanced by NTP treatment (phenolic sheet–polyester film barrier and 3 min exposure), showing 1.4–2.6-fold higher values than the control, confirming the results of the laboratory assays. Although NTP markedly increased the shoot dry matter production of the pasture, which was related to higher tiller population density and greater tiller weight, it did not affect the forage quality of the plants grown in the field. We conclude that NTP technology is suitable to improve seed germination of Gatton panic, in turn leading to improvements in seedling establishment and biomass production under field conditions without compromising forage quality.

Forage performance and cattle production as a function of the seasonality of a Brazilian tropical region

This study aimed to evaluate forage yield, tiller population density, canopy height, nutritional value as well as cattle performance in alternate stocking from three tropical forage cultivars. The experiment followed a randomized block design, in a 3 x 3 factorial scheme with three replications. Three forage cultivars (Marandu, Massai and Xaraés) distributed in nine hectares were evaluated in three dry season periods (transition wet/dry, dry, and end of dry season), with repeated measures over time. The following variables were evaluated: canopy height, leaf: stem ratio, forage mass, leaf mass, stem mass and dead material mass. Total digestible nutrients, crude protein and in vitro dry mass digestibility were evaluated regarding forage nutrition. Animal performance, using 36 eleven-month-old animals (half-blood Nelore), was evaluated by the daily average gain and weight gain by area. During pre-grazing, canopy height presented interaction among forage cultivars and the evaluated periods. The average daily gain showed no interaction among cultivars and period of the year the similarity in animal performance among the cultivars Marandu and Massai show that the Massai grass can be used as an alternative for forage diversification under an alternate management system.

Morphogenesis of stockpiled Marandu, Piatã, Xaraés and Paiaguás brachiariagrass cultivars

ABSTRACT The objective this study was to identify differences in the morphogenic patterns of four Urochloa brizantha cultivars (marandu, piatã, xaraés and paiaguás grasses) during the stockpiling period. A completely randomized design was used, with three replications, in experimental plots of 9m². The evaluations took place over 2 years. The grasses were stockpiled for 92 (Year 1) and 95 (Year 2) days. The leaf appearance rate of paiaguás grass was higher, compared to other grasses. In Year 1, the stem elongation rate of xaraés grass was higher than other grasses. At the end of stockpiling period of Year 1, the tiller population density (TPD) was higher in the paiaguás grass, intermediate in the xaraés and marandu grasses and lower in the piatã grass. At the end of the stockpiling period in Year 2, TPD was higher in the paiaguás grass canopy, intermediate in the marandu and piatã grasses canopies, and lower in the xaraés grass canopy. Paiaguás grass has greater leaf growth during the stockpiling period and is therefore suitable for use under stockpiled grazing. Xaraés grass has high stem elongation during the stockpiling period, which is why its use under stockpiled grazing must be accompanied by adjustments in pasture management.

Management options to recover perennial ryegrass populations and productivity in run-out pastures

In parts of the upper North Island, farmers frequently report perennial ryegrass (Lolium perenne L.) pastures failing within 3 or 4 years post-sowing. This appears to be related to interactions between several factors: climatic (drier, hotter summers), biotic (insect pest), soil (texture, water-holding capacity) and grazing management factors that vary spatially and temporally. The efficacy of three management interventions for recovering ryegrass populations and production in runout pasture was assessed in an experiment initiated in 2018/19 in central Waikato. Treatments were a long-spring rotation (LSR), a longer grazing deferral during late spring and summer (pasture deferral, PD) and under-sowing with perennial ryegrass (US), each applied to pastures of four ryegrass cultivars. In the year after the treatments were implemented, the yield of ryegrass in PD was 2.4 t DM/ha greater than for the control (7-year-old pasture), and ryegrass tiller populations initially doubled but later declined. Yields in US and LSR were intermediate but not significantly different from the control. Ground score changes responded more positively to PD compared with the other treatments. Relative to the baseline prior to initiation of the study, tiller populations increased for PD and US but declined for control and LSR. There were no interactions between management treatment and cultivar for any of the variables measured. Pasture deferral shows promise as an intervention for recovering failing ryegrass pastures through natural reseeding. However, the longevity of the benefits observed here has yet to be determined.

Canopy structural variations affect the relationship between height and light interception in Guinea Grass

The study of canopy structures is essential for the precise management of local forage. Although the relationship between the canopy height (CH) and light interception (LI) allows the best use of forage, there are other characteristics of the canopy that, if not observed, can lead to errors in grazing management. This study analyzes the effect of the defoliation frequencies (DF) and season on the productive and structural characteristics of Guinea grass and defines whether tiller population density (TPD) should be considered in the mathematical models that relate CH to LI. The experimental design used includes randomized blocks with six defoliation frequencies (DF) of 14, 21, 28, 35, 42, and 49 days, over three seasons: rainy season 2015 (RS2015), dry season (DS), and rainy season 2016 (RS2016), in the Amazon biome. Yield characteristics and forage structure were evaluated. The interaction between the DFs and seasons in all evaluated variables included forage accumulation, proportions of stem, leaves and dead material, tiller population density (TPD), CH, LI, and leaf area index. The curve steepness constant (CSC) of the nonlinear models between CH and LI was different from that of the DFs. A DF of 14–28 days averaged a TPD of 616 tillers m−2 and CSC of 0.0407, and a DF of 35–49 days averaged a TPD of 496 tillers m−2 and CSC of 0.0368. An agreement index (d) of 0.87, a bias of 1.5 %, and a determination coefficient (R²) of 0.6187 were obtained for the model that estimated a CH with the inclusion of LI and TPD when validated with data from studies published in the literature. TPD associated with CH and LI allowed for more precise management of the ideal defoliation moment.

Herbage accumulation and tillering dynamics of ‘Zuri’ guineagrass under rotational stocking

AbstractUnderstanding the effects of grazing management on tillering dynamics of forage grasses may help identify management practices that optimize pasture production, stability, and ultimately, persistence. The objective of this research was to evaluate the effects of two grazing frequencies (regrowth interrupted when the canopy was 70 cm tall or at 95% canopy light interception [LI]) and two grazing intensities (reduction of 29 [lenient] or 57% [standard] of initial canopy height) in ‘BRS Zuri’ guineagrass [Megathyrsus maximus (Jacq.) B.K. Simon & S. W. L Jacobs (syn. Panicum maximum Jacq.)], under rotational stocking and on herbage accumulation rate (HAR), tiller appearance rate, tiller mortality, tiller survival rate, tiller stability index (SI), tiller population density (TPD), tiller mass (TM), apical meristem height, and tiller half‐life during two summer rainy seasons in Piracicaba, Brazil. The experimental design was randomized complete block, with a 2 × 2 factorial arrangement. The HAR was not affected by treatments in the first year, averaging 100 kg dry matter ha−1 d−1, but was greater under lenient than standard grazing (146 and 81 kg dry matter ha−1 d−1, respectively) in the second year. In both years, there were no treatment effects on TPD and TM. The use of 95% LI associated with standard defoliation increased the variability in SI. Great tiller population renewal indicated by short tiller half‐life, varying from 31 to 75 d, classifies Zuri as an exploitative cultivar. Zuri guineagrass maintained tiller SI under the grazing treatments imposed but had greater HAR under lenient grazing.

Coinoculaton of endophytic diazotroph with PGPR and AM fungi for enhancing sugarcane production

The field experiment was conducted at Sugarcane Research Station, Cuddalore during 2010 – 2012, to evaluate the response of sugarcane variety CoC 24 to the application of bioinoculants viz., Gluconoacetobacter diazotrophicus, AM fungi and Azophos (Azospirillum and phosphobacteria), under different levels of N, P2O5 and K2O inorganic fertilizer in plant and ratoon crop. The results revealed that the application of mycorrhizae, G. diazotrophicus, Azospirillum and phosphobacteria significantly produced higher cane yield in plant crop. The application of Gluconoacetobacter diazotrophicus @10 kg + AM fungi + Azophos @10 kg + 75 % NPK recorded the maximum germination and tiller population and also maximum mean millable cane population of 1.32 lakhs /ha, cane yield (137.45 t/ha) and sugar yield (16.96 t/ha). Similar results were recorded with the ratoon crop. The population of Azospirillum and Pseudomonas are higher compared to that of Glucanoacetobacter diazotrophicus and phosphobacteria. The application of bioinoculants improves soil microbial biomass and their by enhancing soil organic matter content. The applied bacterial sources helps in nitrogen fixation and also in continuous mobilizing and solubilisation of nutrients and their persistence and colonization in soil is an added advantage and also enhances the soil fertility. The usage of these bioinoculants inturn reduces the inorganic fertilizer input and thereby reduces the cost of cultivation.

Effects of timing of nitrogen fertilizer application on responses by tropical grasses

Timing of nitrogen (N) fertilizer application can influence grass regrowth, so it is important to identify how tropical grasses respond to delays in applying fertilizer after defoliation. Our objective was to identify the effects of timing of N fertilizer application after harvest on the productive, morphogenic and structural characteristics of 3 tropical grasses: ‘Xaraés’ (Urochloa brizantha [Hochst. ex A. Rich.] Stapf cv. Xaraés), ‘Marandu’ (Urochloa brizantha [Hochst. ex A. Rich.] Stapf cv. Marandu) and ‘Tanzânia’ (Megathyrsus maximus [Jacq.] cv. Tanzânia). The experiments were performed in a greenhouse, in a completely randomized design, with 5 delays in applying N after harvesting (0, 3, 6, 9 and 12 days). Delaying fertilizer application did not affect the forage mass of Xaraés and Marandu palisade grass (7.4 and 7.8 g/pot, respectively). There was a linear decrease in number of leaves per tiller and leaf appearance rate, but tiller population density and phyllochron increased linearly as fertilizer application was delayed. Grass forage mass (12.2‒10.6 g/pot), number of leaves per tiller (3.1‒2.6 leaves/tiller) and forage accumulation rate (0.47 to 0.41 g DM/d) of Tanzânia guinea decreased linearly as N application was delayed, but tiller population density was unaffected (25 tillers/pot). Based on our results, N fertilizer should be applied to Tanzânia guinea grass pastures as soon as possible after harvest and certainly before 3 days, while there is not the same urgency with Xaraés and Marandu where fertilization could be delayed up to 12 days without significant detriment. These suggestions need to be tested in a field study before being recommended widely.

Unexpected larval habit of Listronotus bonariensis (Coleoptera: Curculionidae) raises questions about population dynamics analysis and management

AbstractListronotus bonariensis (Kuschel) is a pest of agriculturally important graminaceous species, with mining larvae that kill the stems of the host plants. In this study, larval populations were measured in spring and summer in irrigated dairy grassland comprising Lolium perenne L. (cv. Nui) with and without the endophyte Epichloë festucae var. lolii Latch, M.J. Chr. and Samuels and Poa annua L.. Larvae were extracted from tillers taken from the swards of these two grass species and extracted from turves, and L. bonariensis population densities were estimated from tiller and turf larval counts on a m−2 basis. Over the study period, the total number of larvae and larval densities extracted from turves was on average 2× greater than indicated from tillers. In most seasons, larval densities from turves were significantly higher than those from the tillers, though there was no correlation between tiller and turf larval densities. Mean head capsule widths of larvae emerging from turf samples showed significant seasonal effects compared with tillers, while mean head capsule widths of all four instars were significantly greater when extracted from tillers compared with turves. There was a significant endophyte effect on head capsule widths of larvae collected in summer, but the effect was not consistent across instars or source. Conversely, no significant endophyte effect on head capsule width was found in spring populations from either tillers or turves. This study shows that in irrigated dairy pasture, a high proportion of L. bonariensis larvae can live externally of tillers, presumably among the organic matter around the base of grasses in irrigated dairy pasture, and that density estimates based only on tiller populations will have significantly underestimated actual numbers. Having a precise indication of larval population densities is essential when developing life tables or determining economic damage threshold levels.

The exclosure cage technique revisited: Pasture responses under continuous stocking and their relationship with estimates of forage accumulation in grazing experiments

AbstractForage accumulation (FA) is a key response in grazing experiments, and estimates of FA in continuously stocked pastures are often obtained using exclosure cages. This study evaluated how 14‐, 21‐, and 28‐d exclusion periods using cages affected morphological, physiological, and morphogenetic responses of continuously stocked ‘Mulato II’ hybrid brachiariagrass (Brachiaria spp. syn. Urochloa spp.) pastures maintained at 20‐ and 30‐cm canopy height and how this affected estimates of FA. Grazing exclusion resulted in greater rates of leaf elongation (LER; 1.62 vs. 1.37 cm tiller−1 d−1), stem elongation (SER; 0.16 vs. 0.07 cm tiller−1 d−1), leaf growth (101 vs. 86 kg dry matter [DM] ha−1 d−1), and stem growth (3.4 vs. 1.8 kg DM ha−1 d−1) inside the cages compared with outside. Greater LER resulted in greater final leaf length and leaf area index (LAI) in longer exclusion periods. With greater LAI, photosynthesis was greater within the exclosure cages than on pasture (54.5 vs. 43.9 μmol CO2 m−2 s−1). Greater leaf growth rate, together with same tiller population density and leaf senescence rate (LSR) across exclusion periods, resulted in overestimated FA by 14, 26, and 24% for 14‐, 21‐, and 28‐d exclusions, respectively. There was no effect of canopy height on FA, because greater LER and SER values in 30‐cm canopies were compensated by greater LSR. Choice of sites for cage placement by visual appraisal and reduced number of sampling sites resulted on “negative” values of calculated FA for the 14‐d exclusion, making the choice of sampling sites a major source of error in estimation of actual FA. Increasing the number of sampling sites and using indirect measurements of forage mass (FM) may increase the accuracy of FM and FA estimates.

Pasture and animal production in silvopastoral and open pasture systems managed with crossbred dairy heifers

The objective of this study was to evaluate the pasture traits and performance of crossbreed dairy heifers in a silvopastoral system (SPS) and open pasture (OP) of Urochloa decumbens, after 14-years of management. In the SPS, an average reduction of 46% in the photosynthetically active radiation (PAR) was calculated in relation to the OP. Experimental design was a randomized complete block, with three replications and two treatments (SPS and OP), evaluated in two seasons (summer and autumn), during three years. The paddocks were managed under continuous stocking with Holstein × Gyr heifers. The herbage mass was greater in OP, but a greater leaf and lower dead material percentages were observed in the SPS. The OP had higher tiller population than SPS only in the first year. The herbage accumulation was higher in the OP during autumn; however during summer only a trend was observed. The crude protein content was greatest in SPS, while the fiber constituents and forage digestibility did not vary with system. The stocking rate was greater in OP in the second year and similar between systems in the other years. Average daily gains were similar between systems, regardless of season and experimental year, while the OP showed a greater gain per area in the third experimental year. Despite of the difference in some variables, after 14–16 years of establishment, it was observed only a small decrease in the animal productive per area in SPS in the last year, in relation to OP, which indicates a high resilience of SPS, even under intense shading.

Height and mowing of pasture at the end of winter modulate the tillering of Marandu palisadegrass in spring

In pastures subjected to stockpiling, the tiller population goes through an intense process of self-thinning, hindering the recruitment of new tillers in the subsequent season. We evaluated different pasture management strategies in late winter in an attempt to modify tiller recruitment during spring. Urochloa brizantha cv. Marandu was maintained at 4 different levels (heights) of stockpiled pasture at the end of winter: short (15.1 cm), medium (23.2 cm), tall (31.4 cm) and tall/mown (31.3 cm, mown to 8 cm). In October (early spring), the short and tall/mown pastures had a tiller appearance rate (TAR) and a population stability index (PSI) superior (P<0.05) to that of the tall pasture. During the remainder of the growing season, these characteristics (TAR and PSI) were similar for all pastures. Tiller survival rate (TSR) was also highest (P<0.05) in short pasture in early spring. TAR values were highest in early spring and these tillers persisted throughout the growing season. When stockpiling Marandu palisadegrass pasture during spring it is important to have it short at the end of winter to ensure early and intense tillering in spring. If pasture is tall at the end of winter mowing at this time before spelling is advantageous.

Growth of Megathyrsus maximus cv. Mombaça as affected by grazing strategies and environmental seasonality. I. Tillering dynamics and population stability

In rotationally grazed pastures, the canopy light environment can be modulated through both grazing frequency and severity, and the magnitude of sward responses may differ according to forage species and its ability to use available resources. We hypothesised that the tall, tufted, fast-growing, tussock-forming species Mombaça guineagrass (Megathyrsus maximus (Jacq.) B.K.Simon & S.W.L.Jacobs cv. Mombaça) can modulate its tillering dynamics and change its persistence pathway according to grazing strategy and the availability of growth factors. Treatments corresponded to all combinations of two levels of pre-grazing canopy light interception during regrowth (95% and maximum) and two post-grazing heights (30 and 50 cm), and were allocated to experimental units according to a randomised complete block design with four replications. Measurements were performed throughout contrasting climatic conditions during four seasons from January 2001 to February 2002. A quite stable tiller population density presented regardless of the range of grazing frequency and severity used in the study. However, tiller appearance and death were strongly influenced (P < 0.001) by season of the year, with highest rates recorded during the two summers and lowest during autumn–winter. There was no conclusive evidence that the persistence pathway of Mombaça guineagrass changes within the grazing management strategies studied.

Phosphorus fertilization in the implantation of a silvopastoral system: morphogenic and structural characteristics of Mombaça grass

ABSTRACT The objective of this study was to evaluate the effect of phosphate fertilization on morphogenic and structural characteristics of Mombasa grass under conditions of implantation of silvopastoral system with eucalyptus and monoculture in the Amazon/Cerrado ecotone. The experiment was conducted at UFT-EMVZ during the rainy seasons of the 2016/2017 and 2017/2018 agricultural years. The experimental area was subdivided into two cultivation systems, Mombaça grass monoculture, with 0.25 hectare and silvopastoral system, intercropping eucalyptus with Mombaça grass, with 0.75 hectare area. The design used was a 4 x 2 factorial IHD with four doses of phosphorus (0; 50; 100; 200 kg.ha -1 P2O5 year-1) and two cultivation systems (monoculture and silvopastoral) with three repetitions. Three cycles were evaluated for an average rest period of 21 days. Weekly measurements were taken to evaluate structural and morphogenic characteristics of plants. In general, factors tested such as phosphorus fertilization, cultivation system and year (implantation and following year) showed influence, altering the development of Mombaça grass, reflecting on the morphogenic and structural characteristics. Tiller population density, crop growth rate, leaf area index showed interactions between phosphorus fertilization and the cultivation systems analyzed (P <0.05). Phosphorus fertilization used in the implantation, moment of greatest requirement of the plant, influenced forage development by increasing the crop growth rate, leaf appearance, as well as leaf and stem elongation in the two evaluated systems.

Defoliation intensity and leaf area index recovery in defoliated swards: implications for forage accumulation

This study evaluated the leaf area index (LAI) recovery mechanisms and forage accumulation rates on the regrowth of different grass species subjected to different defoliation intensities. For that purpose, plots of Pennisetum clandestinum (kikuyugrass), Lolium multiflorum (annual ryegrass), and Avena strigosa (black oats) were defoliated from 20 to 80 % of their initial heights (25, 20, and 25 cm, respectively). At different increments in height, forage samples were collected to ground level and used to estimate tiller population density (TPD), leaf area per tiller (LA), and forage mass. From these data, we calculated the leaf area index (LAI), average leaf area index (aLAI), and average and instantaneous forage accumulation rate (FAR and IFAR, respectively). Data were plotted over time (days) to describe LAI recovery and forage accumulation rates. As the defoliation intensity increased, greater canopy heights were needed for pastures to achieve their maximum forage accumulation rates, which required longer regrowth intervals. The need for high tiller recruitment after defoliation, which delayed canopy LAI recovery, seemed to be one of the main cause. Thus, grazing management strategies that involve costly tiller recruitment could decrease both overall forage production and sward persistence over time. However, the plant ability to recover LAI after successive intense defoliations seems to be species-dependent and related to their phenotypic plasticity.